Finned tube



E. G. LEHMAN FINNED TUBE Filed Feb. 17., 1933 Sept. 4, 1934.

S2 Ml :Suventor Gttornegs fatwa/zdf Gv. La/mmv Patented Sept. 4,l 1.934

PATENT OFFICE FINNED TUBE Edward G. Lehman, York, Pa., assignor to York f Ice Machinery Corporation, York, Pa., a corporation of, Delaware Application February 17, 1933, Serial No. 657,283

4 Claims.

This invention relates to heat exchange elements and particularly to spirally finned tubing.v

It has heretofore been proposed to provide pipes or tubes with' external fins wound in a progressive 5 spiral, and these fins are commonly produced by forming transverse tapering flutes in a strip of sheet metal, the tapering formation of the flutes causing the strip to coil in a progressive spiral around the pipe, the wide bases of the flutes contacting the pipe wall and producing a stable structure. The flutes are formed in the metal strip substantially as it reaches a point of tangency with the pipe. The form of the flutes is such as to ,cause the spiral fin to cling closely to the pipe.

It has also been proposed to cut pipe into lengths and galvanize them inside and out with the fin in position, a hot dippingprocess being used. The effect of the galvanizing treatment is to connect the fin and the pipe by a thin film of metal.

In cutting the pipe into lengths it is the practice to sever and remove the end portions of the fin, leaving 'end portions of the pipe exposed for connection,V and this cutting operation is customarily performed before the pipe is galvanized. K

It follows from this practice that the end portions of the remaining iin are insecurely fastened to the pipe or tube and become disarranged in the galvanizing treatment, frequently producing ,an unmerchantable product. The purpose of the present invention is to overcome this difficulty by providing a simple retainer which can be applied, prior to the galvanizing step, and which remains in place after the pipe and iin have been galvanized, as stated. This retainer acts to hold the fin 30 in place during the galvanizing treatment, and forms a permanent retainer and end finish for the finned pipe section.

The preferred embodiment of the invention will be described in connection with the accompanying 40 drawing, in which,-

Fig. 1 is an elevation of a section of finned pipe with one retainer in its final clamped position and the other retainer about to be forced to position. This second retainer is shown partly in section.

Fig. 2 is an axial section of the finished product.

In the manufacture of the product a length of pipe 6 is provided with a spiral iin structure 7, formed of a strip of metal which has deep corrugations 8 at its inner edge, the corrugations extending transversely of the strip and tapering so that they disappear at the outer edge 9. The formation of these corrugations, as the strip is fed to the pipe, causes the strip to curl edgewise in aspiral. around the pipe and cling closely thereto. Thisl practice is well known in the art.

aperture with a flange 14 extending away from After the pipe 6 has been provided with the spiral fin as described, the fin may be cut away at the ends of the pipe to expose portions 11 for connection' to a fitting, manifold, or the like.

This connection may be made by threading, or

'in any other known manner, and since this is hot a feature of the invention, no threads or other connections are shown.

If short sections are to be used, the finned pipe is cut into appropriate lengths and the iin is re- 'rnoved for appropriate distances at the ends. It is found that when the fin is cut back the clinging tendency of the end portions of the fin on the pipe is somewhat impaired so that the end convolutions of the fin are apt to become disarranged and irregular in spacing. To prevent this I force over each end of the pipe a retainer 12, here shown as a disk having a peripheral iiange 13 extending toward the fin, and a central the iin. The opening and the ange 14 are so formed that the edge of the flange 14 tends to bite the pipe as the retainer is forced to place and holds the retainer disk against retrograde movement. After the disk has been forced to place (see the position of the upper flange in Fig. 1) the fin 7 is wrapped closely around the pipe-with its convolutions properly spaced and a portion of the peripheral iiange 13 is bent inward, as indicated at 15, to clamp the end portion of the fin 7.

A disk 12 is mounted at each end, as shown in Fig. 2, and clamped to the corresponding end of the tin 7. The effect is to lock the terminal convolutions of the fin 7 in place firmly. Then the pipe and ln are galvanized inside and out by a hot dipping process. The effect is to coat the n, the pipe and the disk retainers with a thin film of metal, say zinc, which provides a bond between the pipe, on the one hand and the fin and retainers on the other hand, and between the retainers on one hand and contacting portions of the iin on the other hand. The resulting product is characterized by firm attachment of the fin to the pipe, accurate spacing of the convolutions of ,the iin, and the presence of a desirable reinforce and protecting disk at each end of the spiral fini While I prefer the construction illustrated in the drawing, it is obviously possible to modify the form of the retainer disks, without departure from the spirit of the invention.

What is claimed isz- 1. A finned heat exchange element comprising in combination a tubular member; a. separately formed fin of sheet metal coiled therearound in a progressive spiral in edge engagement with said 110 tubular member; and at least one terminal mem ber encircling and engaging said tubular member and having a peripheral flange overhanging said lin, at least a portion of said flange being bent into clamping engagement with an end portion of said n.

2. The combination of claim 1, further characterized in that said terminal member comprises a disk having a ange directed oppositely to said peripheral flange and encircling a central aperture in the disk, the last-named flange entering into clamping relation with the tubular member.

3. A nned heat exchange element comprising in combination, a tubular member; a separately formed lin of sheet metalhaving transverse tapered corrugations which cause the n to embrace the tubular member closely when coiled therearound in a progressive spiral; and dislilike retainers encircling the tubular member in close engagement therewith, each retainer having a peripheral flange portion in clamping engagment with an end of said iin.

4. A nned heat exchange element comprising in combination, a tubular member; a separately formed fm of sheet metal having transverse tapered corrugations which cause the fin to embrace the tubular member closely when coiled therearound in a progressive spiral; disk-like retainers encircling the tubular member in close engagement therewith, each retainer having a peripheral flange portion in clamping engagement with an end of said fin; and a protecting film of metal connecting said tubular member, lin and retainers.

' EDWARD G. LEHMAN. 

